Hello Linda, You are right on both counts - razor clams, like all bivalves, are filter feeders. And they typically live buried in sand or mud, with just the anterior tip of the shell extending above the surface of the sediment, or sometimes completely buried. Ensis and Solen are true razor clams (also called jackknife clams), in the family Solenidae. Pharus, though it is long and slender, is a member of a different family, Solecurtidae, which also includes such genera as Solecurtus, Tagelus, Azorinus, etc. Razor clams are rapid burrowers. More than one collector, after having dug a number of specimens out of the mud, has dumped them out of the bucket in shallow water, to wash them off, only to have them all disapper into the mud again before they could be re-collected. Their digging action can also pull them through the water, so they can actually swim fairly rapidly for a short distance. Ensis and Solen are edible, but not commonly offered on the commercial marketplace. Paul M.